<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .pink {
            background-color: pink;
        }
    </style>
</head>

<body>
    <button class="pink">按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
<script>
    let but = document.querySelectorAll('button'); 
    //不能在外部获取pink元素，外面获取的永远是第一个按钮的元素
    for(let i = 0; i <= but.length; i++){
        but[i].addEventListener('click',function(){
        document.querySelector('.pink').className = ''
        this.className = 'pink'
        
    })
}
</script>
</body>
</html>